Add -xg and xn to exclude tests based on some character string in
the name or group.

To get better info when the assert is in a helper function:

1) if the test case file and the file where the error is are different, 
print two error lines one pointing to the test case and the other 
to the assert

2) if the failure line number is before the test case line number, 
print two error lines one pointing to the test case and the other 
to the assert


